The fight over coal trains in the Pacific Northwest pulls into Seattle on Thursday.

Several thousand people will gather at the Washington State Convention Center to offer their thoughts on plans to export Rocky Mountain coal to Asia through ports in Washington and Oregon.

So many people are expected that the hearing already has been postponed once. The hosts — Whatcom County, the state Department of Ecology and the U.S. Army Corps of Engineers — knew they needed a bigger venue.

“Everything about this comment period has been unprecedented … at least as far as the scope of interest and participation,” said Ecology spokesman Larry Altose.

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While there are at least five proposals to build shipping terminals in Washington and Oregon to ferry coal from Wyoming and Montana to energy-hungry Asia, Thursday’s hearing is, ostensibly, about just one. A subsidiary of SSA Marine wants to construct a port outside Ferndale, known as the Gateway Pacific Terminal, to ship 48 million tons of coal abroad each year.

Already, more than 9,000 people from Friday Harbor to Spokane have testified at hearings or written letters, some in support of new terminal jobs but most expressing concern about everything from increased traffic caused by long coal trains to the climate-change impacts of sending cheap fossil fuel to China.

The interest is especially unusual when you consider the government is only taking input about what it should consider during an environmental review of the project. That review could take two more years.

“I think it’s a really passionate issue,” said Kelly Enstrom, who works for a public-relations firm that represents businesses, politicians and labor groups supporting the terminal proposal. Her group says the terminal would create jobs, boost trade and promote a U.S. resource in Asia that they could otherwise get from Australia.

“Supporters believe we can protect the environment and we can do this right,” she said.

Dan Jaffe isn’t so sure. The professor of atmospheric and environmental chemistry at the University of Washington Bothell is trying to analyze air pollution generated by a potential increase in trains carrying coal. Still, he said, “speaking for myself, I think it’s not at all a good idea. It’s the wrong direction for us to be going in — for the planet, the state, the region.”

One of the central questions of the debate is whether the federal government will evaluate the impacts of each project separately — or whether it will also examine the cumulative environmental consequence of bring up to 140 million tons of coal through Washington and Oregon to be burned in Asia.

While opponents, led by environmental and climate-action groups, have spent the last two years rallying opposition to coal exports, pro-coal supporters are now engaged, too.

In previous hearings across the state, where testimony was first-come, first-served, some opponents arrived hours in advance and held spots for like-minded colleagues. Some supporters, in turn, paid people to stand in line to make sure their representatives got to testify. This time, the three agencies hosting Seattle’s hearing will switch to a lottery system. On Thursday, they’ll let those in attendance enter random drawings at the top of each hour of the three-hour event for a total of about 150 two-minute speaking slots. The agencies also will accept written comments.

Gateway supporters, including the Association of Washington Business, some unions and the mayor of Ferndale, want each project studied independently. Environmentalists, the governor of Oregon, the Department of Ecology and Seattle city leaders have urged the Corps to consider the cumulative impact of all the proposals.